Evaluation Board User Guide
ADXRS450 - UG
Rev. 0 | Page 11 of 17
NOISE AND ROOT ALLAN VARIANCE
Figure 20: Noise and Root Allan Variance Panel
The software GUI includes the ability to calculate and plot the
Root Allan Variance of the ADXRS450. Root Allan Variance
can be approximately described as the variation of successive
long term averages of the null output of the ADXRS450. This is
usually reported in units of “degrees per hour”, and indicates
the long term bias stability of a gyroscope. In order to generate
an accurate Root Allan Variance plot, it is recommended that
this test be run (at least) overnight, during which time care
should be taken to ensure that the device is in a temperature
stable, and disturbance-free environment. Any rotational rate
input into the gyroscope can greatly degrade the validity of the
resulting RAV-plot.
Determining the RMS noise of the ADXRS450 can be done on
this same panel. The evaluation GUI calculates the RMS noise
by taking the standard deviation of the specified number of
points, which is roughly equivalent to the 1-sigma peak to peak
noise value. These data points are obtained at a 500Hz data
rate. It is recommended that the user perform this test with at
least 16,000 data points in order to obtain accurate results. Less
data points can be used, but the reported RMS noise will be
subject to higher variability.
